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  • rivers  (2)
  • 36C; CALYPSO; Calypso Corer; Greenland Rise; IMAGES V; Marion Dufresne (1995); MD114; MD99-2227  (1)
  • COMPUTER PROGRAMMING AND SOFTWARE  (1)
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  • 1
    facet.materialart.
    Unknown
    Nd and Pb isotope signatures of the clay-size fraction of sediment core MD99-2227
    PANGAEA
    In:  Supplement to: Fagel, Nathalie; Hillaire-Marcel, Claude; Humblet, Marc; Brasseur, G; Weis, D; Stevenson, R (2004): Nd and Pb isotope signatures of the clay-size fraction of Labrador Sea sediments during the Holocene: Implications for the inception of the modern deep circulation pattern. Paleoceanography, 19(3), PA3002, https://doi.org/10.1029/2003PA000993
    Details
    Publication Date: 2023-06-27
    Description: Nd and Pb isotopes were measured on the fine fraction of one sediment core drilled off southern Greenland. This work aims to reconstruct the evolution of deep circulation patterns in the North Atlantic during the Holocene on the basis of sediment supply variations. For the last 12 kyr, three sources have contributed to the sediment mixture: the North American Shield, the Pan-African and Variscan crusts, and the Mid-Atlantic Ridge. Clay isotope signatures indicate two mixtures of sediment sources. The first mixture (12.2-6.5 ka) is composed of material derived from the North American shield and from a "young" crustal source. From 6.5 ka onward the mixture is characterized by a young crustal component and by a volcanic component characteristic of the Mid-Atlantic Ridge. Since the significant decrease in proximal deglacial supplies, the evolution of the relative contributions of the sediment sources suggests major changes in the relative contributions of the deep water masses carried by the Western Boundary Undercurrent over the past 8.4 kyr. The progressive intensification of the Western Boundary Undercurrent was initially associated mainly with the transport of the Northeast Atlantic Deep Water mass until 6.5 ka and with the Denmark Strait Overflow Water thereafter. The establishment of the modern circulation at 3 ka suggests a reduced influence of the Denmark Strait Overflow Water, synchronous with the full appearance of the Labrador Seawater mass. Our isotopic data set emphasizes several changes in the relative contribution of the two major components of North Atlantic Deep Water throughout the Holocene.
    Keywords: 36C; CALYPSO; Calypso Corer; Greenland Rise; IMAGES V; Marion Dufresne (1995); MD114; MD99-2227
    Type: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
  • 2
    Electronic Resource
    Electronic Resource
    A comparison of natural and human determinants of phytoplankton communities in the Kentucky River basin, USA (1995)
    Springer
    Hydrobiologia 297 (1995), S. 201-216 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; cell densities ; chl a ; taxonomic composition ; rivers ; Kentucky ; stream size ; land use ; nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Physical, chemical, and biological characteristics of the Kentucky River and its tributaries were assessed for one year to compare effects of seasonal, spatial, and human environmental factors on phytoplankton. Phytoplankton cell densities were highest in the fall and summer and lowest in the winter. Cell densities averaged 1162 (± 289 SE) cells m1−1. Cell densities were positively correlated to water temperature and negatively correlated to dissolved oxygen concentration and to factors associated with high-flow conditions (such as, suspended sediment concentrations). Chrysophytes, diatoms, and blue-green algae dominated winter, spring, and summer assemblages, respectively. Ordination analyses (DCCA) indicated that variation in taxonomic composition of assemblages was associated with stream size as well as season. Spatial variation in phytoplankton assemblages and effects of humans was investigated by sampling 55 sites in low flow conditions during August. Phytoplankton density increased with stream size. Assemblages shifted in composition from those dominated by benthic diatoms upstream to downstream communities dominated by blue-green algae and small flagellates. Human impacts were assumed to cause higher algal densities in stream basins with high proportions of agricultural or urban land use than in basins with forested/mined land use. While density and composition of phytoplankton were positively correlated to agricultural land use, they were poorly correlated to nutrient concentrations. Phytoplankton diversity changed with water quality: decreasing with nutrient enrichment and increasing with conditions that probably changed species composition or inhibited algal growth. Human impacts on phytoplankton in running water ecosystems were as great or greater than effects by natural seasonal and spatial factors. Our results indicated that phytoplankton could be useful indicators of water quality and ecosystem integrity in large river systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00019285
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Seasonality in river phytoplankton: multivariate analyses of data from the Ohio River and six Kentucky tributaries (1989)
    Springer
    Hydrobiologia 182 (1989), S. 99-114 
    Details
    ISSN: 1573-5117
    Keywords: seasonality ; phytoplankton ; rivers ; Kentucky ; Ohio River ; monitoring data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two years of physical/chemical and algal abundance data obtained from national Stream-Quality Accounting Network records of 10 river sites in Kentucky USA (4 Ohio River sites and 6 Ohio River tributaries) were analyzed to determine how seasonal changes in river phytoplankton related to changes in physical and chemical parameters. Phytoplankton assemblages differed among rivers as a function of drainage basin characteristics, but exhibited common seasonal changes related to temporal variation in the physical/chemical environment. Distinct shifts in algal dominance were identified between spring (March, April), late summer (July, August, September), and transitional (May, June, November) periods in the 10 systems. Nine common algal genera were found to differ in their response to changes in physical or chemical parameters. Abundances of Anacystis, Oscillatoria, Scenedesmus, and Melosira were strongly positively correlated with temperature while Chlamydomonas and Navicula abundances were inversely related to temperature. Other physical/chemical factors that were significantly positively ( + ) or negatively ( - ) correlated with algal abundances included discharge and alkalinity (Oscillatoria, +), pH CChlamydomonas and Cyclotella, (both + ), turbidity (Anacystis, \s- ; Navicula + ), silica (Cyclotella, - ), and ammonium/organic N (Anacystis, -). Genera within the same algal division exhibited different seasonal patterns and responded to different physical/chemical parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00006036
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    Paper (German National Licenses)
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  • 4
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    Unknown
    Capabilities and applications of the Program to Optimize Simulated Trajectories (POST). Program summary document (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The capabilities and applications of the three-degree-of-freedom (3DOF) version and the six-degree-of-freedom (6DOF) version of the Program to Optimize Simulated Trajectories (POST) are summarized. The document supplements the detailed program manuals by providing additional information that motivates and clarifies basic capabilities, input procedures, applications and computer requirements of these programs. The information will enable prospective users to evaluate the programs, and to determine if they are applicable to their problems. Enough information is given to enable managerial personnel to evaluate the capabilities of the programs and describes the POST structure, formulation, input and output procedures, sample cases, and computer requirements. The report also provides answers to basic questions concerning planet and vehicle modeling, simulation accuracy, optimization capabilities, and general input rules. Several sample cases are presented.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-2770
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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